Set-verify-guards-eagerness may be thought of as an event that
merely sets a flag to 0, 1, or 2. The flag is used by
certain defunevents to determine whether guard verification is
tried. The flag is irrelevant to those defunevents in
:program mode and to those defunevents in which an explicit
:verify-guards setting is provided among the xargs. In the
former case, guard verification is not done because it can only be
done when logical functions are being defined. In the latter case,
the explicit :verify-guards setting determines whether guard
verification is tried. So consider a :logic mode defun in
which no :verify-guards setting is provided. Is guard
verification tried? The answer depends on the eagerness setting as
follows. If the eagerness is 0, guard verification is not tried.
If the eagerness is 1, it is tried iff a :guard is explicitly
provided in the defun. If the eagerness is 2, guard
verification is tried.

The default behavior of the system is as though the
:verify-guards-eagerness is 1. The current behavior can be
ascertained by evaluating the form
(default-verify-guards-eagerness (w state)).